1. Field of the Invention
This invention relates to a cable retainer for holding a flexible cable and more particularly relates to a chain cable retainer comprising a plurality of same-size link members longitudinally connected to each other so that the respective link members can be rotated with respect to each other.
2. Description of the Related Art
In an apparatus, e.g., an industrial robot or the like, having a movable part moving in relation to a body, it is often necessary to electrically connect the body to the movable part. In such a case, if the electrical cable connecting the body to the movable part was left without protection, the electrical cable can come in touch with other members and could be damaged, cut or broken.
Therefore, in a conventional technique, when a cable is used to connect a body with a movable part, the cable is accommodated in a flexible cable retainer formed as, for example, a continuous chain to protect the cable. Such a chain cable retainer is constituted in such a manner that the retainer can be deformed when there is a relative movement between the body and the movable part, so that it is possible to protect the electrical cable from the external environments without restricting the movement of the movable part.
A cable retainer as mentioned above is disclosed in Japanese Unexamined Utility Model Publication (Kokai) No. 62-200836. In this prior art, the link members constituting the chain cable retainer have a so-called closed structure to improve the protection of an electrical cable.
In the above-mentioned prior art, as shown in FIGS. 5 and 6, a chain cable retainer 50 is constituted by connecting a plurality of link members 52, one by one, in a longitudinal direction. However, if one end of the cable retainer is fixed to the body and the other end is fixed to the movable part, it is necessary to mount special fixing latches 53 and 55, which have shapes different from that of the link members 52 constituting the body of the cable retainer 50, on the ends of the cable retainer 50. Since the cable retainer 50 is constituted by continuously connecting the same-size link members 52, the connecting structure at one end (at A in FIG. 5) of the cable retainer is different from that at the other end (at B in FIG. 5) thereof, so that it is necessary to prepare two kinds of latches 54 and 56 suitable for the respective ends of the cable retainer.
Consequently, in the prior art, the cable retainer needs one kind of the link member 52 constituting the body of the cable retainer and the two kinds of latches 54 and 56 for fixing both ends of the cable retainer 50. Thus, it is necessary to prepare three kinds of parts. Due to the production of a plurality of different parts, it is necessary to prepare a plurality of dies for forming the respective pieces and thus there is a problem that the cost of production of cable retainer is increased.
Further, in the prior art, there is another problem as follows. Generally, the link members 52 are continuously connected to each other in a longitudinal direction to produce a chain cable retainer as shown in FIG. 5. For this end, each link member 52 has a pair of side plates 60 connected to a bottom plate 58 (at the opposite sides of the bottom plate 58) and facing each other. The side plates 60 can be opened to allow a pair of cylindrical projections 62 arranged at the rear end of the link member 52 to slidingly move along the inner walls of the side plates 60. Thus, the projections 62 are engaged with hole 64 arranged at the front of the side plates 60. Thus the link members 52 are connected to each other.
In such a connected structure of the link members 52, if the side plates 60 and the bottom plate 58 were made thicken to increase the rigidity of the link members, when the link members 52 were connected to or disconnected from each other, a strong force would be required to open the side plates 60. Thus, there is a problem that, without special tools, the link members 52 cannot be connected to or disconnected from each other.
In the above-mentioned prior art, there is still another problem. Each link member 52 is provided with restricting means 53 (FIG. 6) for restricting the angle through which the link member 52 can be pivotably moved with respect to the adjacent link member 52. The angle restricting means 53 comprises a pair of recesses 55 provided at front ends of the link members 52 and a pair of tongues 57 provided at the rear end of the link member 52 and engaged with the recesses 55. Thus, the link member 52 can be pivotably moved, around the projections 62, between two positions in which the upper and lower ends 57a and 57b of the tongue 57 come into contact with upper and lower inside walls 55a and 55b, respectively. The pivot angle of the link member 52 is thus restricted in a range of .beta.-.alpha. in FIG. 6. Therefore, the cable accommodated in the cable retainer is protected in such a manner that the radius of curvature of the cable cannot become too small and the cable is not damaged.
However, in the prior art, as shown in FIG. 6, the link member 52 is provided with the angle restriction recesses 56. Therefore, the mold for producing the link members is so complicated that the manufacturing cost for the link member increases and, therefore, the cable retainer may be expensive as a whole.